Vitamin maker sold for $3.8 billion

NEW YORK (CNNMoney.com) -- Nutritional supplement maker NBTY will be acquired by private equity firm Carlyle Group in a deal valued at $3.8 billion, the companies announced Thursday.

Under the merger agreement, NBTY (NTY) shareholders will receive $55 a share, a 57% premium to NBTY's average closing share price in the 30 trading days ended July 14. The last time NBTY's stock price touched $55 was in February 2007.

Shares of NBTY were up more than 44% in premarket trading, at $54 a share.

NBTY's board of directors have approved the merger, which is subject to regulatory and shareholder approval. The deal is expected to close by the end of 2010.

"We will leverage Carlyle's global resources and consumer sector knowledge to further drive the company's global growth," said NBTY chairman and chief executive Scott Rudolph, in a statement.

Sandra Horbach, the managing director of Carlyle and head of the consumer and retail sector team, said she "impressed" by NBTY's business and looks forward to helping the company grow.

The Ronkonkoma, N.Y.-based company offers more than 22,000 products under its own name, as well as third-party brands including Nature's Bounty and Vitamin World. It previously said it had a "roller coaster" year in 2009, when annual income fell by 5% to $146 million.

But the company's performance for the first half this year has been strong. During the fiscal second quarter, NBTY's profit almost doubled to $47 million, thanks to improved sales and a higher gross profit, the company said.